共查询到20条相似文献,搜索用时 31 毫秒
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The rate of [3H]dopamine binding to crude synaptic membranes from canine caudate nucleus was considerably increased by 2 mM ATP, 5′-adenylylimidodiphosphate and GTP or by 1 mM 5′-guanylyl-imidodiphosphate, while strongly inhibited by 2 mM ADP and GDP. Half maximal concentrations of [3H]dopamine to bind to the membranes were 1.11 × 10?7M and 8.75 × 10?6M in the absence of 4 mM ATP, indicating a negative cooperativity of the dopamine receptor, and 9.25 × 10?7 M in its presence. Hill coefficient was increased from 0.70 to 1.04 by addition of 4 mM ATP. The optimal concentration of ATP for [3H]dopamine binding was in the range of 0.5 to 5 mM. 相似文献
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S Watabe A Terada T Ikeda H Kouyama S Taguchi N Yago 《Biochemical and biophysical research communications》1979,89(4):1161-1167
Bovine spleen cathepsin D is activated by polyphosphate anions when bovine serum albumin is used as substrate at pH 4.6. In the presence of ATP at 10 mM, the catheptic activity at this pH is enhanced as high as 17 times over the control. Similar activating effects were observed, though to varying degrees, with sodium tripolyphosphate, nucleotides, nucleotide analogues, CoA, polyU and yeast RNA. The possible mechanism and biological significance of the activation were discussed with regard to the intralysosomal polyanionic substance. 相似文献
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[3H] -Concanavalin A binding to brain particulate preparations measured by a filtration technique was found to show a characteristic regional specificity with the caudate-putamen area exhibiting the greatest density of concanavalin A (con A) binding sites. The synaptic membranes were shown to be the most highly enriched of the subcellular fractions examined in terms of lectin-binding glycoproteins. Con A was also shown to inhibit the basal adenylate cyclase activity of cerebral, cerebellar, and caudate-putamen particulate preparations in a concentration-dependent manner. This lectin sensitivity of the adenylate cyclase is apparently an intrinsic property of the enzyme complex since a detergent dispersed preparation of the cerebral cortical enzyme was equally inhibited by con A. It is proposed that one of the membrane con A binding sites in brain tissue is a component of the adenylate cyclase system. 相似文献
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S Takemoto K Okamoto I Takeuchi 《Biochemical and biophysical research communications》1978,80(4):858-865
The addition of cyclic AMP to the shaking medium of cells disaggregated from pseudoplasmodia of suppressed the accumulation of cell-bound phosphodiesterase which normally occurs (1) after disaggregation. The suppression was not secondarily brought about by its possible inhibitory effect of cyclic AMP on protein synthesis or by its stimulating effect on the release of the enzyme into the medium. The effect was reversible and specific to cyclic AMP. On the other hand, the inhibitory effect of cyclic AMP on the disaggregation-induced inactivation of UDP-galactose transferase was not apparent in the initial period, but thereafter it slowed down the decrease in the enzyme activity. These results indicate that exogenous cyclic AMP mimics at least in part the regulatory effects of cell-to-cell contact on certain enzymes. 相似文献
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The sarcolemmal membranes isolated from rat skeletal muscle are capable of incorporating 32P from [γ?32P]ATP. The membrane protein phosphorylation requires Mg2+. Cyclic AMP, cyclic GMP and their dibutyrul derivatives showed no marked effect on sarcolemmal phosphorylation.The Mg2+-dependent 32P labeling was significantly enhanced by Na+. The rate of Na+ -stimulated 32P incorporation was quite rapid reaching steady state levels within 5 s at 0 °C. K+ reduced the Na+ -stimulated 32P-incorporation but enhanced the 32Pi release. This inhibitory effect of K+ on Na+ -stimulated 32P incorporation was prevented by the cardiac glycoside, ouabain.The Na+ -dependent 32P labeling showed substrate dependency and the Na+ site was saturable. The apparent for ATP was 2 · 10?5 M. The optimum pH for 32P labeling was between 7 and 8.Na+ -dependent membrane phosphorylation showed a direct relationship with the (Na+ + K+ATPase activity. The high turnover rate of 32P intermediate (12 000 min ?1) suggested its functional significance in the overall transport ATPase reaction sequence.The predominate portion (> 90%) of the phosphorylated membrane complex was sensitive to acidified hydroxylamine and to alkaline pH suggesting an acylphosphate nature of the phosphoprotein.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that 32P incorporation occurred predominately into a 108 000 dalton subunit which is a major protein component of sarcolemmal membranes. A very low level of 32P incorporation was also observed into a 25 000 dalton subunit and Ca2+ slightly enhanced the phosphorylation of this component.The size () and some properties of the sarcolemmal phosphoprotein are closely similar to other (Na+ + K+ATPase preparations reported so far. 相似文献
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A rapid fluorogenic method for the demonstration of 5′-nucleotide phosphodiesterase in human serum has been developed. This method uses the substrate 4-methylumbelliferyl 5′-thymidylate impregnated in agarose gels or filter paper strips. Zymograms are developed in less than 30 min at 25°C, and the sensitivity of this method has been compared with that of the indigogenic method. 相似文献
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Luminal brush border and contraluminal basal-lateral segments of the plasma membrane from the same kidney cortex were prepared. The brush border membrane preparation was enriched in trehalase and γ-glutamyltranspeptidase, whereas the basal-lateral membrane preparation was enriched in (Na+ + K+)-ATPase. However, the specific activity of (Na+ + K+)-ATPase in brush border membranes also increased relative to that in the crude plasma membrane fraction, suggesting that (Na+ + K+)-ATPase may be an intrinsic constituent of the renal brush border membrane in addition to being prevalent in the basal-lateral membrane. Adenylate cyclase had the same distribution pattern as (Na+ + K+)-ATPase, i.e. higher specific activity in basal-lateral membranes and present in brush border membranes. Adenylate cyclase in both membrane preparations was stimulated by parathyroid hormone, calcitonin, epinephrine, prostaglandins and 5′-guanylylimidodiphosphate. When the agonists were used in combination enhancements were additive. In contrast to the distribution of adenylate cyclase, guanylate cyclase was found in the cytosol and in basal-lateral membranes with a maximal specific activity (NaN3 plus Triton X-100) 10-fold that in brush border membranes. ATP enhanced guanylate cyclase activity only in basal-lateral membranes. It is proposed that guanylate cyclase, in addition to (Na+ + K+)-ATPase, be used as an enzyme “marker” for the renal basal-lateral membrane. 相似文献
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Gerard Lefebvre Nicole Martin François Schneider Guy Raval Robert Gay 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,540(2):221-230
Cultures of Nocardia restricta, a prokaryote from the group of Actinomycetes, can be synchronised by diluting, in a fresh growth medium, cells already in stationary phase. The synchronisation of the cultures is monitored by examining the synchrony of DNA replication.In these synchronised cultures, the intracellular cyclic AMP level exhibits rythmic oscillations with a period equal to the generation time of the culture. There is only one peak per generation. The average ratio of maximum to minimum concentrations is at least 3.Cyclic AMP accumulates also in the medium with a step pattern. It appears in the medium during maximum production of cyclic AMP in the cell.The specific activity of adenylate cyclase (EC 4.6.1.1) measured in the 30 000 × g pellet of cell-free extracts also oscillates and correlates well with fluctuations in the cyclic AMP level. At the end of exponential growth, cyclic-AMP phosphodiesterase (EC 3.1.4.17) is detectable in the cells. The specific activity of this enzyme measured in the 30 000 × g supernatant of cell-free extracts shows also an oscillating pattern.To our knowledge it is the first time that such oscillations in the metabolism of cyclic AMP are described among prokaryotes. It is now possible to look at a link between this phenomenon and the cell cycle of the organism. 相似文献
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Rat liver cytosol binds 3H-cAMP and 3H-DBcAMP . Fractionation of bound radioactivity by DEAE-Sephadex chromatography shows that 3H-cAMP is associated with a different cytosolic protein than is 3H-DBcAMP. The pI's of the cAMP-protein and the 3H-DBcAMP-protein complexes are 6.7 and 3.9, respectively. Competition studies between 3H-cAMP and its structural analogues have shown the following order of effectiveness in competing for binding sites in rat liver cytosol: cAMP > N6-MBcAMP > O2′-MBcAMP. No inhibition of 3H-cAMP binding was observed with 5′-AMP, adenosine, cGMP or DBcAMP. binding experiments with rat serum has shown that only 3H-DBcAMP binds to any significant extent. 相似文献